<p>Honeycomb Sandwich Plates with Elastic Supports (HSPEs) are widely employed in aerospace, construction, and marine engineering due to their lightweight design, high strength, and vibration isolation capabilities. In this study, a composite spring-shell cell model is proposed for analyzing the geometrically nonlinear behavior of sandwich panels containing arbitrarily distributed internal and edge elastic supports. The equivalent elastic parameters are obtained based on the homogenization method, the nonlinear constitutive equations are constructed by combining the third-order shear deformation theory with the Green–Lagrange strain tensor, and the unit stiffness matrix is derived by the principle of virtual work. The elastic support stiffness is further superimposed on the unit stiffness matrix of the sandwich panel to form the overall stiffness matrix of the HSPE system. The accuracy of the proposed method in predicting displacement responses is verified by comparison with finite element method results. In addition, the coupled effects of boundary conditions, geometrical parameters, internal support locations and stiffness, and transversely distributed loads on the nonlinear bending behavior of rectangular honeycomb sandwich panels are systematically investigated. It is shown that the model can accurately capture the local and global deformation characteristics under different support conditions, which provides an efficient analysis tool for the engineering design and optimization of HSPEs.</p>